This invention is directed to an apparatus and method for gasifying solid organic materials to convert the chemical energy store in such materials to thermal energy or gaseous products that may serve in biochemical and/or chemical synthesis for further product development. The novel apparatus specifically relates to a new and novel gasification chamber.
It has long been recognized that many industrial and agricultural solid organic by-products, such as forestry and agricultural residue, and the like, are a potential source of large amount of chemical energy. The substantial increases in the cost of traditional fuels, such as fuel, oil and natural gas, which occurred during the 1970's, have provided substantial economic incentive to try to develop effective and efficient techniques for recovering the energy in these organic by-products, energy that traditionally was not recovered to any substantial extent. Such organic materials, frequently referred to as “biomass” materials, are now successfully utilized to some extent as fuel in some very large industrial systems, for example, in firing the power boiler and the recovery boiler in a pulp or paper mill. However the high capital cost that has heretofore been associated with biomass energy recovery systems has precluded their successful use in small or even medium size energy recovery systems. Medium size energy recovery systems, that is, of the size from about 4,000,000 to 8,000,000 BTU/hr., are used in community centers, schools, nursing homes, and small industrial and commercial establishments and, to date, biomass fuels have not been satisfactorily utilized as fuel in heating systems for such facilities. Among the U.S patents that have issued on inventions relating to the recovery of energy from wood chips or similar organic materials are for example, U.S. Pat. No. 5,138,957 that issued to Morey, et al. on Aug. 18, 1992; U.S. Pat. No. 4,184,436 that issued to Palm, et al. Jan. 22, 1980; U.S. Pat. No. 4,312,278 that issued to Smith, et al. on Jan. 26, 1982; U.S. Pat. No. 4,366,802 that issued to Goodine on Jan. 4, 1983; U.S. Pat. No. 4,321,877 that issued to Schmidt, et al on Mar. 30, 1982; U.S. Pat. No. 4,430,948 that issued to Schafer, et al. on Feb. 14, 1984; U.S. Pat. No. 4,593,629 that issued to Pedersen, et al. on Jun. 10, 1986; U.S. Pat. No. 4,691,846 to Cordell, et al. that issued on Sep. 8, 1987, and U.S. Pat. No. 4,971,599 that issued to Cordell on Nov. 20, 1990. However, it is not known that any of the inventions described in these patents have been successfully adapted to recover biomass energy on a cost-effective basis in small and medium size energy recovery systems.
Thus, gasifiers are not new in the art and there are many publications dealing with such pieces of equipment and systems in which they are used, but by way of illustration, attention can be directed to U.S. Pat. No. 4,691,846 that issued on Sep. 8, 1987 to Cordell, et al, in which there is described a method and apparatus for gasifying solid organic materials in which the system is described in detail with emphasis on the hopper and its manner of operation. It should be noted that the gasifier is shown and described as a dome-like structure with a bottom feed mechanism for the solid organic materials, and an upper exhaust system to remove the gaseous effluent to a secondary chamber.
A second disclosure can be found in U.S. Pat. No. 6,120,567 that issued on Sep. 19, 2000 to Cordell, et al in which there is described a method of gasifying solid organic materials and in which a similar apparatus and system as is disclosed in the '846 patent is set forth. The '567 patent is related to the '846 patent. Again, it should be emphasized that the gasifier is shown and described as a dome-like structure having a bottom feed and an upper exhaust for the gaseous effluent.
The major concerns with these early devices and systems is that the primary gasification chamber cylindrical and is therefore severely limited in the manner of construction to accommodate large volumes of through-put without consuming larger areas of floor space. Another concern is the need to dump ash on a continuous basis to avoid swings in the chemical composition of the producer gas. Moreover, the gasifier of the prior art does not have any basins and thus it is impractical to build up and maintain a hearth.